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采用聚苯胺包覆法合成了具有核壳结构的纳米LiFePO_4/C复合材料。聚苯胺包覆层对限制先驱体FePO_4的粒径起着关键性的作用。反应热力学理论计算和实验结论都表明制备FePO_4/PANI最适宜的pH值约为5。FePO4/PANI复合物的粒径由苯胺添加量决定,当添加的苯胺与FePO_4摩尔比为0.44时,可以合成粒径约50 nm的FePO4/PANI复合物。经过碳热还原过程,FePO_4表面的聚苯胺层转化为LiFePO_4表面导电性良好的碳包覆层。采用优化工艺合成的LiFePO_4/C颗粒近似球体,粒径约为55 nm,碳包覆层厚度约为2 nm,0.2和1 C倍率下放电比容量约为136 mAh.g~(-1),在10、20、30和40 C倍率下放电比容量分别为118,103,94和87 mAh·g~(-1),高倍率下放电比容量和循环性能明显优于固相法合成的LiFePO_4材料。.
Nanometer LiFePO 4 / C composite with core-shell structure was synthesized by polyaniline coating. The polyaniline coating plays a key role in limiting the particle size of the precursor FePO 4. Theoretical calculations of thermodynamics and experimental conclusions show that the most suitable pH for preparing FePO4 / PANI is about 5. The size of FePO4 / PANI composites is determined by the addition of aniline. When the molar ratio of aniline to FePO4 is 0.44, the size of FePO4 / PANI composites can be synthesized. After the carbothermal reduction process, the polyaniline layer on the surface of FePO 4 is transformed into a carbon coating with good conductivity on the surface of LiFePO 4. The approximate particle size of LiFePO 4 / C was about 55 nm and the thickness of carbon coating was about 2 nm. The specific discharge capacity was about 136 mAh.g -1 at 0.2 and 1 C rates. The specific discharge capacities of 118, 103, 94 and 87 mAh · g -1 at 10, 20, 30 and 40 C were higher than those of LiFePO 4 synthesized by solid state reaction. .